I have a MBP from 2007, with a 160gb hard drive. I'm very tempted to upgrade it to a 500 or 640gb hard drive. I was ready to do so, but then a friend of mine spooked me about doing it myself, by telling me a story about another friend of his who fried his computer trying.
I've checked out the legalities. While changing the HDD won't void the warranty, if you damage something while doing so, applecare won't pay to repair it.
So, I'd like to ask all you fine people who have swapped hard drives in old MBPs, how risky is it? Am I being paranoid, or is there actually a substantial risk of damaging your computer by changing the hdd?
I just did this last weekend, along with upgrading to Snow Leopard, on maybe the same model (2.33 Ghz 15"). It is easy, as others have reported, but it can be frustrating at times.
I also recommend the ifixit site. Print out the instructions and check off the steps.
If you don't already have a larger drive, try macsales.com. I picked up a 320GB, 7200 RPM Seagate with a FW800 external case for under $150. They also sent along the proper tools.
Things to watch out for:
Screws: there are a bunch of them, and some with subtle differences. Take your time with them, and try to keep them separated. Some have only certain places they can go, but others may look the same, but be maybe 1 or 2mm different in length.
Top case front clips: These clips are above the DVD drive, and on either side of the latch. They're a bugger to get loose, and you'll swear you've broken them, but - in my case, at least - they didn't break.
Once I got that loose, the top case fairly flew upward, taking the ribbon connector right off of the socket on the main board. No breakage, but it was a concern. You'll also need to look closely at the board to find the connector, as it looks an awful lot like the ICs on the board.
With the top case off, the HDD is right there, under where your left wrist would rest. First, remove the two screws keeping the drive in the MBP. These are along the inboard side, on a piece of metal looking flat with a round part at each end. Remove the screws, and this metal bar. Then the drive slides inboard to release it. But first, you have to CAREFULLY remove the HDD connector from the mainboard, AND, again CAREFULLY, remove the ribbon from the top of the HDD. The ribbon goes from the main board to the back of the drive (and the drive connector), then to the front of the drive, where the connectors for the BT and IR modules live. Carefully separate that from the drive, and the connector from the back of the drive.
Holding the old drive and new drive in the same orientations, transfer the screws on the sides with the rubber mounting supports from the old to the new, one at a time. Connect the cable to the drive connector, and slip the drive into place, outboard side first. You may need to pull up slightly on the outboard edge of the drive so the mounting supports go into the holes properly. Put the connector back to the main board, and gently tap down the ribbon to the top of your new drive. Then put back the metal piece that holds the inboard side of the drive in place.
Put the top case back on - remembering to put the keyboard/trackpad connector back on, and tape it down. Then align everything, clip the front of the top case down, and put all the screws back in the right places.
Then you get to install the OS or restore from your Time Machine backup!
Good Luck!

